What better occasion could there be for DreamWorks Animation to launch its new 3D initiative than an old-style creature feature, evoking the decade of the first wave of 3D, the 1950s? Monsters vs. Aliens is a cheerfully nostalgic action-comedy smorgasbord of half-century-old genre images, from ruthless space invaders to bizarre mutants to secret government enclaves, with a 50-foot woman as an added bonus.

That unfortunate woman, Susan Murphy (voiced by Reese Witherspoon), is the most modern element of the story conceived by directors Rob Letterman and Conrad Vernon, with four additional credited screenwriters. A fresh-faced California girl about to be married within hours to a self-absorbed local TV weatherman, Susan has the rotten luck to be hit by a meteor containing a strange substance that makes her grow and grow like Lewis Carroll’s Alice. Susan’s ultimate personal liberation, to accompany her liberation from mundane Earthly concerns, is the main driver of the narrative—a canny strategy to attract young ladies to this movie along with all the boys enticed just by the title Monsters vs. Aliens.

Soon after she crashes up through the roof of the church where she was to be wed, Susan is drugged and captured. She wakes up in an austere, eerie clandestine facility, where she soon meets the other “monsters” imprisoned by the government. In a nod to The Fly, there’s Dr. Cockroach (Hugh Laurie), a brilliant but daft scientist whose failed experiment transformed him into a talking insect. The Missing Link (Will Arnett) is a macho half-ape, half-fish who unfortunately left the water during the Ice Age and become frozen for thousands of years. The jolly but easily distracted B.O.B. (Seth Rogen), short for “benzoate-ostylezene-bicarbonate,” is a living gelatinous mass born out of a snack-food lab fiasco. And then there’s Insectosaurus, a 350-foot grub with the disposition of a tiny baby.

This eccentric quintet might have remained top-secret were it not for the arrival of a giant alien robot which violently rejects the friendly overtures of the President (Stephen Colbert), the Close Encounters notes segueing into “Axel’s Theme” from Beverly Hills Cop. Monster-minder General W.R. Monger (Kiefer Sutherland with a hilarious gruff Southern accent) volunteers his motley crew to battle the robot, and Susan (now dubbed “Ginormica”) proves her mettle, with strategic assists from her kooky cohorts, in a frantic showdown in San Francisco. But Gallaxhar (Rainn Wilson), the power-crazed alien behind the robot invasion, doesn’t give up the fight so easily.

Monsters vs. Aliens may not have the elegance and resonance of a Pixar movie, but it’s zany, good-natured fun. Ever the pro, Witherspoon really commits to her vocal performance, making Susan’s surreal plight relatable and generating plenty of empathy. Laurie, Rogen and Arnett are so perfectly cast, you can’t imagine anyone else performing their roles, while Wilson’s special brand of dementia is ideal for the maniacal Gallaxhar. Even the smaller roles are cast from a who’s-who of comedy today: Paul Rudd, Julie White, Jeffrey Tambor, Amy Poehler, etc.

And Renée Zellweger and “The Office”s John Krasinski cameo in a delicious role reversal of the familiar parked-car smooching session/alien encounter.

Though the stop-motion Coraline beat it to theatres, Monsters vs. Aliens is billed as the “first film totally authored in the 3D format.” DreamWorks’ “InTru 3D” process here creates some striking 3D effects, like General Monger in a jet pack hovering above the audience, or Ginormica reaching out her hand in distress. Sometimes the action seems a bit too frenetic for the eyes to catch up, but DreamWorks will surely refine the visual rules as its 3D output continues.

Offering creature mayhem for the boys, female empowerment for the girls, and just enough vintage content for their parents, Monsters vs. Aliens looks like a win for DreamWorks.